I was just talking last week about white-nose bat fungus decimating the northeat North American bat population, and saying if one cave could go from 300,000 bats to 81 bats in three years, obviously some natural mechanism could possibly do the same sort of thing to human beings.

Yup! But it looks like the nature behaves like any other big organization - the left hand doesn't know what the right one is doing. Why develop a killer fungus and erupt volcanos at the same time to slow down the spreading?